This invention relates to tape cassettes and, more particularly, to a tape reel lock formed on a video tape cassette dust door for preventing despooling of tape from the reels, when the cassette is not received by a tape player/recorder.
For convenience of reference, when describing the tape cassette herein, "inward" means in a direction toward to the interior of the cassette from its sides, "outward" means in a direction toward the sides of the cassette from the interior, and "downward" means in a direction toward the base from the cover.
A conventional tape cassette has a relatively flat, is substantially rectangular configuration, formed of a suitable plastic. The cassette includes a base and cover, each having side walls. Tape reels are usually suitably located in side-by-side relation within the cassette so as to be freely rotatable, and a magnetic tape is wound on the tape reels. A reel leaf spring is attached to the cassette cover to normally bias the tape reels downwardly.
These cassettes further include a pivotable, spring biased dust door which, when closed, protects the tape from dust, contact, etc. When the door is outwardly opened, usually by a tape player/recorder when the cassette is placed therein, the magnetic head of the player/recorder can gain access to the tape.
Video tape cassettes also include tape reel locks to prevent unwanted tape reel rotation which causes "despooling" of the tape during shipping, handling, etc. Despooled, tape, of course, can be damaged.
As a tape reel lock, the industry has almost uniformly adopted a multipiece reel lock, such as shown and described in U.S. Pat. Nos. 4,447,020 or 4,232,840. Such multipiece reel locks include a separate actuator/retractor, a pair of separate movable arms for respectively locking the reels, and a separate spring for biasing the arms toward the reels. These reel locks are assembled between the tape reels in walls/receptacles formed at the rear of the cassette base and are actuated by a pin of the tape player/recorder that protrudes through an opening formed at the rear of the base, when the player/recorder is operated.
Of course, such a multipiece lock is expensive to produce and assemble. Further, due to the number of parts and the fabrication requirements for each part, production yields cannot be maximized. Finally, there is always the chance that the parts, such as the spring, could become misaligned during shipping, handling or use, and fail to properly operate.
Assignee's currently pending U.S. Pat. application Ser. No. 389,906, now U.S. Pat. No. 5,056,735, entitled "Video Cassette Integral Actuator/Reel Lock Spring" provides an improved one-piece, biased reel lock to replace the conventional multipiece reel lock, significantly decreasing manufacturing and assembly costs.
There is also known a sliding locking member for certain audio cassettes, such as described in U.S. Pat. No. 4,728,056. More particularly, a substantially planar locking member is spring biased for normally urging protrusions formed inwardly thereon against the tape reel hubs. When the cassette is placed in a tape player/recorder, the locking member is retracted by the tape player/recorder, to remove the protrusions from engagement with the hubs and allow the hubs to rotate.
This type of device also suffers from manufacturing inefficiencies since the locking member must be spring loaded. Further, this type of device may be applicable only to a cassette used in a pulse code modulation system, as described in the '056 patent. Finally, the size, shape and sliding movement of the locking member do not provide much design flexibility for tape cassettes.
As can be seen, the art still is in need of a reel lock which needs no assembly and requires no moving parts or springs, to further simplify structure, improve quality and reliability, and minimize costs.